Hello, I have been having some issues with my ac at home. Normally when a fuse or RCD trips and the appliance is the issue it will be as a result of either a dead short or earth leakage and it will happen every time the product is switched on. I found that the transformer in the air handler is blown along with the 3amp fuse. I have a Carrier furance model number 58STA/STX and my LED is indicating a Secondary Voltage Fuse is Open. After all, replacement fuses are only a few dollars at home improvement stores. They can come loose over time due to the natural vibrations of the unit, so make sure to check the connections. The leading cause of thermal fuse burnout is obstructed airflow. It can be a BC7845 (9430-342) or a BB7841 (9430-338). A good fuse will have nearly zero ohms of resistance, if the fuse is blown there will be no reading. During those hot and muggy summer months, or during those subzero cold winter months, heat pumps can ensure room temperatures are comfortable for your entire family. SIXQJZML 10 Pack F2AL Fast-Blow Fuse 2A 250V Glass Fuses 0.2 x 0.78 inch / 5 x 20 mm (2amp) (F2A) At this point I don't know if it makes any difference, but the GD Parts Lookup website (link on menu bar above) shows two thermostats used in your unit. They can come loose over time due to the natural vibrations of the unit, so make sure to check the connections. RULES for AOP - Owner Assistance and Contractors, The ARPA Zone/Open Membership Discussion Forums, Energy Efficiency and Building Performance Discussion NEW, Carnak Zone/Locked Areas - For Professional Member Only, Pro Forum: Refrigerants and EPA regulations **NEW, Pro Forum: Residential Refrigeration and Appliances **NEW, Pro Forum: Equipment Recalls and Bulletins **NEW, Pro's Forum: Building Science Discussions, Educational Forums - Open for all in the industry, Welcome to HVAC-Talk's Educational Forums, How to Submit Links, Articles and Quiz Questions, Frequently Asked Questions About Submissions, Physics, Thermodynamics, Fluid Flow and Combustion, Educational, Training & Reference Information, Manufacturer's Technical Information Links, Electrical Theory, Circuits and Electronics, HVACR Equipment, Components & Accessories, Accessories � Humidifiers, Air Cleaners, HRUs, Fans, Filters, etc. You need to remedy the issue with your blown fuse and find the underlying cause. Loose wires, in general, are often responsible for blown fuses. The 2 amp fuse in my Coleman-Mach thermostat is blowing. �I haven�t failed. First the thermostat needed batteries, then we were unable to get the unit to blow heat because of fuse blowing. make sure the 3amp fuse is good. My Honeywell Thermostat Says Wait: What to do Next? I have R,W,G,Y wires. I'm wondering if the thermister 8193776 or the high limit thermostat 66156 could be malfunctioning. For instance, you will need to reset a fuse once it's blown. Components � Coils, Heaters, Motors, etc. You may suspect a blown fuse and wonder what you can do to replace it or prevent it from occurring again in the near future. You may also need to use your multimeter to check if your fuses are blown. A faulty transformer or a malfunctioning thermostat wire can all be common culprits for fuses that continue to blow. The furnace requires a lot of electricity to run, and your home may not have the means to support it or there could be a short in the system. The fuse that keeps blowing is a thermal fuse and is caused by low air flow. I am adding a WiFi thermostat. This is my old thermostat. It doesn't call for aux heat during this, but it is a longer duration, combined with a cold morning means a defrost cycle. It is a Potterton HE boiler, and a Honeywell controller. This blows the fuse and the furnace, blowing fan and AC all cease working. You may be able to replace the fuse, swap out your air filters, and fix the problem immediately. My Honeywell Thermostat is Not Turning On. Michael Joseph has more than 20 years of hands-on experience as an avid home handyman and had 10 years in the construction industry, specifically in the field of HVAC. Inspect the area around your furnace for potential leaks. As soon as you request heat the fuse blows and when I try to run the fan to on nothing happens. Winter is knocking at your door, but the furnace refuses to greet it. Blew third fuse. I replace. My best suggestion is to turn everything off at the breaker and use a volt meter to check for continuity between all the thermostat wires. It monitors the temperature of the dryer, and when that temperature gets too high, it shuts power off to the motor (not to the heating element !!!) Participate in over 40 different forums and search/browse from nearly 3 million posts. So it gets cold in the house and I realize I have not heat. You just need to have a multimeter and check continuity between two contacts. Start by making sure that you turn off all electricity running to your unit. This is where the fuse blew, in the airing cupboard. Diagnosing a tripped thermal fuse is easy. Fuse blows. On either type of fuse, you can tell that it is blown when the wire is broken. Check the blower wheel to make sure it isn't broken or clogged up. I have a kenmore 66515834000 diswasher. The potential risk and damage that could result from regularly changing the fuses simply isn’t worth it. Malfunctioning Thermostat Wire If your thermostat wire touches the metal frame of the furnace, this can cause a blown fuse. heat not to kick on during colder temps when our heat pump can't keep up. I removed all the wires going to my thermostat and it would not blow the fuse when powered on. Fuse blows. In your case, you likely have a dead short somewhere in the wiring or a bad load that is going short to ground causing the fuse to blow. Jumper the R and the W on the circuit board for the t-stat. I jumped the wiring on the thermostat and each time, the fuse keeps blowing. It has no issues with fan and cool calls. Accessories � Pumps, Cooling Towers, Evap Condensers, etc, Components � Valves, Motors, Condensers, Evaporators, etc, Duct Systems Design, Installation & Practice, Piping Systems Design, Installation & Practice, Control System Design, Installation & Practice, Welcome from the Editor & Electrical Forum Rules, Pro's Forum: National Electrical Code (NEC), Pro's Forum: Calculations & Electrical Theory, Pro's Forum: Electrical Business & Marketing. If you fix the fuse once and it immediately blows again, you have a much larger problem on your hands that seriously needs to be addressed. Playing detective can be a little tricky, though. I got a new thermostat, the new one that replaces the older model. You need to find the root cause of the blown fuse on the furnace circuit board before you cause damage to the unit. This can spell major problems as the temperatures continue to dip lower and lower with each passing hour. I replace, no problem for a while and then blow. The #1 question asked by NEW MEMBERS. One night when we did need to use the furnace I saw a flash and the new fuse I replaced went. When I attach it to the C terminal on circuit board, it blows the 5 amp onboard fuse. Save my name, email, and website in this browser for the next time I comment. This transformer is located inside your HVAC equipment. I find it really unbelievable that install did not wrap wires with at least electrical tape ( now shrink tape is used) and zip tie wires together so this issue did not occur. If you suspect that the fuse on your furnace has blown, here are the next steps that you need to take to remedy the situation. Gain access to our free AOP (Ask a Professional) Section to get real answers for your questions. Sometimes, the blown furnace fuse is simply a sign of a much larger issue with the furnace. I've completely cleaned the machine including the blower - dismantling the machine to do so. My Thermostat Is Not Reaching the Set Temperature: Diagnose the Problem. The power to your furnace unit simply isn’t turning on. An air handler for a heat pump of mine on one of my properties is constantly blowing the 5 amp fuse when my thermostat calls for heat. This can be the sign of an electrical problem, putting you at risk of a serious fire. The suburban furnace will work fine, the blower comes on then the flame ignites and the heater works just fine until it reaches temperature and it seems to blow the fuse at that time. Whenever I replace the fuse, I replace the companion high limit thermostat. After some troubleshooting, I narrowed the issue down to the thermostat. All of these particles enter into the blower motor and cause the fuse to burn out. I tried several things but noted that the fuse blew even with the thermostat turned down (off). Turn power off at the furnace disconnect the red Thermostat wire at the furnace circuit board. 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